This volume is a collection of papers presented at the Twelfth International Conference on Ultrafast Phenomena held at Charleston, SC, from July 9 to 13, 2000. The Ultrafast Phenomena Conferences are held every two years and provide a forum for discussion of the latest results in ultrafast optics and their applications in science and engineering. A total of more than 200 papers was presented, reporting progress in the technology of generating and characterizing ultrashort pulses, including new techniques for shortening the duration of laser pulses, for stabilizing their absolute phase, and...